Drylands cover approximately 54 million km²,which accounts for 40% of the global land area,and is inhabited by 20% of the human population;however,these areas are increasingly affected by desertification.Desertification is concentrated in the northwestern,northern,and northeastern parts of China (the so-called "Three Norths"):an estimated 3.3 million km² have been affected by desertification,accounting for 34% of China's total land area.Desertification has become a crucial environmental problem at a global scale,and has begun to affect the survival and socioeconomic development of humankind.Research has suggested that both climate and human activities play important roles in the process of desertification,which is complicated and includes complex interactions between human and natural factors (e.g.,climate).However,previous research generally focused on either meteorological factors associated with climate change or factors associated with human activities,and lacked quantitative assessments of their long-term interaction.Thus,the roles of climate change and human factors in vegetation cover change and desertification are uncertain.This creates a high risk of misunderstanding the current situation and adopting ineffective policies and programs to combat desertification.It is,therefore,urgently necessary to comprehensively study the interacting effects.To understand the factors that determine whether mitigation programs can contribute to desertification control and vegetation cover improvement in desertified areas of China,and the complex interactions that affect their success,we used a pooled regression model based on panel data to calculate the relative roles of climate change and human activities on the desertified area and vegetation cover.We used the 1983 to 2012 normalized-difference vegetation index,NDVI,which decreases with increasing desertification.We found similar effect magnitudes for climate change and human activity factors for NDVI:human activity factors were the dominant factor that affected vegetation change,accounting for 58.2%-90.4% of the effects.Climate change accounted for 9.6%-41.8% of the effects on NDVI.Therefore,desertification control programs must account for the integrated effects of both socioeconomic and natural factors.Although humans are clearly part of nature,we are qualitatively different from other parts of nature:our actions have more rapid and disruptive consequences than those of most natural phenomena.Therefore,we must be careful to avoid the adoption of extreme approaches to change natural ecosystems because our changes may occur more rapidly than it is possible for the ecosystems to adapt,and the resulting problems may not be evident immediately but have long-term consequences.Our method for identifying the contributions of each driving factor was defensible for providing a broad overview.This method should be identified in future research to improve the ability of this research to support restoration planning.